1. Field of the Invention
The present invention relates to a vehicle lamp and particularly to a vehicle lamp having an indicative mark such as a recognition mark for identifying itself or a certification mark for indicating that it meets the standard required.
2. Description of the Related Art
Vehicle lamps may be required to have indicative marks such as recognition marks for indicating the kinds and models of the lamps involved or certification marks for indicating that the lamps involved have met the standards. For example, headlamps of two-wheeled vehicles are manufactured so that they correspond with the keep-to-the-left traffic in Britain and with the keep-to-the-right traffic in other European countries and they direct the low beams of headlamps leftward (hereinafter called the leftward light distribution) and also rightward (hereinafter called the rightward light distribution), respectively. Consequently, such a headlamp is required to have a certification mark (E-mark) for indicating that the lighting device conforms to the European standard and in order to discriminate between the leftward light distribution and the rightward light distribution, a light distribution mark in the form of a leftward arrow together with the certification mark is needed to be put in the case of a lighting device for effecting the leftward light distribution. When the certification mark including the light distribution mark (hereinafter referred to as the certification mark inclusive of the light distribution mark in this specification) is thus put on a headlamp, the certification mark of the headlamp for leftward light distribution has to be different from that of the headlamp for rightward light distribution.
Heretofore, two techniques have been employed for putting different certification marks of the sort mentioned above on light devices. The first technique is a technique for stamping a hallmark integrally on the surface of the lens of a lighting device. More specifically, an insert die is used as a part of the die for use in forming a lens. By selecting the insert die for forming a certification mark for rightward light distribution or leftward light distribution, the insert die is set in the die so as to form the lens; otherwise a certification mark is stamped on the surface of a lens by laser marking using a laser beam. In the case of using this technique for showing a certification mark on a headlamp, it is possible to confirm that the headlamp has met the standard by visually recognizing the certification mark formed on the surface of the lens of the headlamp and that the headlamp has proper light distribution characteristics. According to the second technique, two certification marks respectively for rightward light distribution and leftward light distribution are formed together with a lens. Further, a mark for discriminating between the leftward light distribution and the rightward light distribution is stamped or sealed on the body side of a lighting device in which the lens is mounted. When the lens is incorporated into the body of the lighting device, one of the two certification marks of the lens is recognized by reference to an identification mark on the body of the lighting device. Therefore, it is also possible to confirm that the headlamp has met the standard by visually recognizing the certification mark formed on the surface of the lens of the headlamp and that the headlamp has proper light distribution characteristics by reference to the identification mark on the body of the lighting device.
With the application of the insert die for forming the certification mark to the die for forming the lens according to the first technique, a die mark tends to be produced along the periphery of the insert die, thus deteriorating the appearance of the lens. Moreover, since unevenness is produced on the lens because of the certification mark or the die mark, part of the distribution of light transmitted through the area concerned is abnormally refracted, which results in generating glaring light. Further, two kinds of lenses for rightward light distribution and leftward light distribution respectively formed with different certification marks are necessary. Moreover, as different reflectors respectively for rightward light distribution and leftward light distribution are used, the number of parts forming the respective lamps for rightward light distribution and leftward light distribution together with the lenses and reflectors increases. Accordingly, this causes manufacturing and controlling costs to rise. Moreover, the production efficiency is extremely lowered by the use of laser marking. According to the second technique, on the other hand, the problem of deteriorating the external appearance and that of producing glaring light still remains to be solved though one kind of lens is used. As the identification mark for identifying the certification mark is needed to be formed on the body side of the lighting device, the man power required for this process rebounds on an increase in production cost.